On-site medical gas production plant and associated operating method

ABSTRACT

The invention relates to an on-site medical gas production plant ( 100 ) comprising a unit ( 50 ) for purifying gas, such as air, a first vessel (A) for storing purified gas, and a main gas line ( 10 ) fluidically connecting the gas purification unit ( 50 ) to the said first storage vessel (A). It furthermore comprises a three-way solenoid valve (VA) arranged on the main gas line ( 10 ) upstream of the first storage vessel (A), and furthermore connected to the atmosphere (at  12 ) via a vent line ( 11 ), as well as an operating device ( 4 ) which controls at least the three-way solenoid valve (VA), and at least a first gas analysis device (D 1 ) of which a first measurement line ( 29 ) is fluidically connected (at  28 ) to the main line ( 10 ), upstream of the three-way solenoid valve (VA), and which is electrically connected to the said operating device ( 4 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 (a) and (b) to European Application No. 12155272.3 filed Feb. 14, 2012, the entire contents of which are incorporated herein by reference.

BACKGROUND

The invention relates to a plant for medical air production on-site, that is to say in a hospital building or the like, employing a three-way solenoid valve adapted to discharge product gas contaminated by impurities to the atmosphere via a purge line connected to one of the ports of the solenoid valve, and to a method for controlling or operating such a plant.

The medical air used in hospitals, clinics, treatment centres, emergency or incident units, or the like, for patients' respiration is a medicament whose composition is specified by the European Pharmacopoeia.

More precisely, medical air is ambient air compressed to a pressure above atmospheric pressure, typically several bars, or to tens or even hundreds of bars and containing (by volume) from 20.4% to 21.4% oxygen, at most 500 ppm CO₂, at most 5 ppm CO, at most 1 ppm SO₂, at most 2 ppm NO and NO₂, at most 67 ppm water and at most 0.1 mg/m³ oil; the oil vapours possibly present essentially come from the compression of the air.

It should be noted that, other than oxygen, the components mentioned above (i.e. COx, NOx, water, or oil etc.) are in fact impurities whose presence is tolerated within the limits of the Pharmacopoeia but which ideally are not present therein.

Medical air furthermore contains nitrogen, and may also contain other compounds, such as argon.

Currently, medical air is delivered to hospitals or the like in three forms, namely, depending on the case:

-   -   direct delivery in the form of compressed air, for example at an         absolute pressure of from 200 to 300 bar, in cylinders, that is         to say bottles or canisters of gas, or containers comprising a         plurality of bottles;     -   production on-site by mixing oxygen and nitrogen so as to create         nitrogen/oxygen mixtures, and     -   direct production on-site from ambient air treated, in         particular, by compressors and filtration/purification systems.

Of these, the production of air directly on-site by compressors and filtration systems is the most widespread solution. Such a method is described, for example, in the document EP-A-864818.

The ambient air is taken in and compressed by compressors to a pressure range extending from 1 bar to 80 bar relative. This compressed air is then filtered, that is to say purified, by means of one or more treatment steps, for example by a set of filters and/or by employing a pressure swing adsorption method (PSA).

The medical air produced in this way may be stored in one or more intermediate buffer vessels, then sent through the network of pipes which passes through the hospital building in order to provision the treatment rooms, bedrooms or the like with medical air. It is quite clearly possible, and even indispensable in certain cases, to carry out intermediate expansion of the gas, for example in order to change from a pressure of about 10 bar in the storage vessel to a pressure of 5 or 8 bar in the network.

In general, any break in medical air provision is overcome by using medical air taken from a reserve or backup source in which the air is kept in gaseous form.

The other medical gases used in hospitals or treatment centres, such as oxygen, are also delivered in a similar way to the air. The compositions of these other gases are also specified by the European Pharmacopoeia.

Thus, oxygen may also be produced on-site by a PSA method by using specific adsorbents, such as lithium-exchanged zeolites X, making it possible to retain the nitrogen contained in the air and thus produce gaseous oxygen having a purity typically greater than 90%, or even 93% by volume, as is known from the document EP-A-297542.

However, the methods for producing medical air or other medical gases used on-site (also referred to as on-site methods) present certain drawbacks.

First, these methods do not permit easy monitoring of the reliability of the manufacturing process.

Thus, when an on-site medical air production unit is operating autonomously, the manufacturing process is not overseen continuously and the interventions on the plant take place on the basis of planning, that is to say preventive maintenance, or when an error or a problem arises in the plant, that is to say curative maintenance.

These interventions are therefore carried out independently of the status of the plant and its reliability, which is not optimal because they are carried out either too soon, and therefore without actual need, or too late, and therefore with an impact on the production process and possibly on the final product.

Next, pollutant blockages in the main pipe occur when the gas produced is not compliant. This is because in existing plants, the control solenoid valve is a so called “2-way” solenoid valve which is arranged on the main line.

Although it makes it possible to stop possible pollution upstream of the valve, this pollution nevertheless remains blocked in the main line and necessitates a total purge of the system upstream of the valve. This is not ideal because it entails a shutdown of the gas production and manual intervention.

Furthermore, in the event of short-term breaks in the air provision due, for example, to temporary contamination at the inlet, the backup source is resorted to directly. However, this poses a problem because the backup volume is limited and therefore, if the frequency of the breaks in provision is high, there is then a risk of draining the backup source. In other words, it would be highly beneficial to be able to avoid this drawback by reducing the extent to which the backup source is used, so as to increase its autonomy over time.

Lastly, the air produced by the current methods and plants is in general neither analyzed nor validated in pharmaceutical terms, which may raise obvious problems of compliance and quality. Furthermore, when it is analyzed, in the event of “noncompliance” this usually leads either to immediate interruption of the production and changeover to a backup source air, which may entail overuse of the backup air liable to cause a possible total break in the air provision, or to continuous provision of noncompliant air and parallel triggering of an alarm in order to warn the user, who then needs to intervene manually. It will be understood that these solutions are not ideal either.

In summary, there is currently no method of validating air produced on-site which makes it possible to ensure that the air produced is in fact compliant with the required specifications and which makes it possible to ensure effective and reliable provision of medical air.

In other words, the problem which arises is to provide a plant for continuous on-site production of a medicament gas, particular medical air, in accordance with good manufacturing practice (GMP) and a method for controlling or operating such a plant, which permit in particular:

-   -   supervision of the reliability of the manufacturing process with         rapid detection of any anomaly,     -   monitoring of the various production steps and in particular the         final production with, for each step, the possibility of a purge         thus making it possible to stop any contamination or         noncompliance of the gas produced, in particular medical air,         and/or     -   the use of the backup sources to be reduced to a minimal level.

SUMMARY

The solution of the invention is a plant for on-site production of medical gas, in particular medical-quality air, comprising:

-   -   a gas purification unit adapted to produce a purified gas from a         supply gas,     -   a first vessel for storing purified gas, and     -   a main gas line fluidically connecting the gas purification unit         to the said first storage vessel so as to supply the said first         storage vessel with purified gas coming from the gas         purification unit,

characterized in that it furthermore comprises:

-   -   a three-way solenoid valve arranged on the main gas line between         the gas purification unit and the said first storage vessel, and         furthermore connected to the atmosphere via a vent line,     -   an operating device which controls at least one three-way         solenoid valve,     -   at least a first gas analysis device of which a first         measurement line is fluidically connected to the main line,         upstream of the three-way solenoid valve, and which is         electrically connected to the said operating device,

and in which the operating device is designed and adapted to act on the three-way solenoid valve in response to a signal received from the gas analysis device, so as to allow the gas present in the main pipe to pass to the vent line when the signal received from the gas analysis device corresponds to a “contamination” signal of the main pipe, and simultaneously to prevent any gas being sent to the said first storage vessel.

Depending on the case, the plant of the invention may comprise one or more of the following technical characteristics:

-   -   the gas compression unit supplies the gas purification unit with         a gas to be purified, compressed to a pressure higher than 1 bar         absolute.     -   the gas compression unit supplies the gas purification unit with         compressed ambient air.     -   the gas compression unit comprises at least one screw, piston,         scroll or diaphragm compressor.     -   the gas compression unit comprises a plurality of compressors,         in particular arranged in parallel.     -   the gas purification unit comprises at least one adsorber, each         containing at least one bed of at least one adsorbent material,         preferably at least 2 adsorbers arranged in parallel.     -   the gas purification unit comprises at least one adsorber         operating in a cycle of the PSA type.     -   the gas purification unit comprises at least two adsorbers         operating alternately, and the operating device is designed and         adapted to act on the gas purification unit and/or the gas         compression unit so as to stop any production of gas by the         adsorber which was in operation at the time when the gas         analysis device transmitted the “contamination” signal of the         main pipe to the operating device.     -   the “contamination” signal corresponds to a given level of at         least one impurity, in particular one or more impurities         selected from water vapour, or oil vapours, SOx, COx and/or NOx.     -   the “contamination” signal corresponds to a preset threshold         level, for example corresponding to a maximum level set by the         European Pharmacopoeia as regards the aforementioned impurities         (i.e. water and oil vapour, SOx, COx and/or NOx) or a maximum         limit value lower than the said corrected maximum values (for         example 80% or 90% of the maximum value in the Pharmacopoeia),         which makes it possible to ensure an operational safety margin.     -   the operating device is designed and adapted to act on the         three-way solenoid valve in response to a signal received from         the gas analysis device, so as to stop any gas present in the         main pipe from passing to the vent line when the signal received         from the gas analysis device corresponds to a “compliant gas”         signal of the main pipe, and simultaneously to allow gas to be         sent to the said first storage vessel.     -   the gas purification unit furthermore comprises one or more         filters.     -   the gas purification unit, in particular the adsorbers, makes it         possible to eliminate all or some of the impurities which are         possibly present in the ambient air to be purified or which have         been introduced therein during the compression, in particular         water vapour, oil vapours, SOx, COx and/or NOx, so as to produce         a medical gas compliant with the Pharmacopoeia, in particular         medical air compliant with the European Pharmacopoeia.     -   the valve is a 3-way solenoid valve, of which one of the ports         is fluidically connected via a vent line to the atmosphere and         the other two ports are fluidically connected to the main line.     -   the valve is a solenoid valve controlled by an operating unit,         preferably the operating unit electrically connected to the         three-way solenoid valve.     -   The gas compression unit comprises one (or more) gas inlets         supplied with atmospheric air.     -   the main line connects the first vessel for storing purified gas         to at least one gas consumer site, preferably a network of pipes         in a hospital building     -   the main gas line comprises a second vessel for storing purified         gas, located between the first storage vessel and the said at         least one gas consumer site. The first and second vessels are         therefore arranged in series on the main line.     -   the main gas line branches downstream of the first storage         vessel into a secondary line fluidically connected upstream to         the said main line and downstream to at least one gas consumer         site, that is to say directly or indirectly, for example by         being connected to the main gas line, the said secondary gas         line comprising a third vessel for storing purified gas. The         first and third vessels are therefore also arranged in series,         whereas the second and third vessels are arranged in parallel on         the main line and the secondary line, respectively.     -   it furthermore comprises a backup line fluidically connecting a         backup source, such as a reserve or store of medical air, to the         said at least one gas consumer site, either directly or         indirectly by being connected to the main gas line or the said         secondary line.     -   it furthermore comprises at least 2-way solenoid valves are         typically 2-way solenoid valves, arranged on the main line or         the secondary line, with a first solenoid valve arranged between         the first vessel and the second vessel for storing purified gas,         and a second solenoid valve arranged between the first vessel         and the third vessel for storing purified gas,     -   it furthermore comprises at least two-way solenoid valves,         arranged on the main line and the secondary line, with a third         solenoid valve arranged downstream of the second vessel and/or a         fourth solenoid valve arranged downstream of the third vessel,     -   it furthermore comprises a first purge line, fluidically         connected upstream to the main line and downstream to the vent         line, the first purge line preferably being fluidically         connected to the main line downstream of the second vessel.     -   it furthermore comprises a second purge line fluidically         connected upstream to the secondary line and downstream to the         vent line, the second purge line preferably being fluidically         connected to the secondary line downstream of the third vessel.     -   the first purge line comprises a fifth solenoid valve and/or the         second purge line comprises a sixth solenoid valve.     -   it comprises at least a first gas analysis device, the first         measurement line of which is fluidically connected to the main         line, upstream of the three-way solenoid valve,     -   it comprises a second gas analysis device, of which at least one         second measurement line is fluidically connected to the main         line and/or to the secondary line.     -   the second measurement line comprises a seventh and/or an eighth         solenoid valve.     -   the operating unit furthermore controls the gas purification         unit, the gas compression unit, one or more of the solenoid         valves and the gas analysis device or devices.     -   it comprises one or more nonreturn valves arranged on all or         some of the pipes or lines conveying the gas.

The invention also relates to a method for operating an on-site medical gas production plant, in particular a plant according to the invention as described above, comprising the steps of:

a) producing a purified gas from a supply gas, in particular atmospheric air compressed to a pressure greater than atmospheric pressure (i.e. >1 atm),

b) transporting the purified gas obtained in step a) by means of a main gas pipe,

c) storing at least a part of the purified gas in a first vessel the storing the gas supplied by the gas pipe,

characterized in that it furthermore comprises the steps of:

d) determining in the main gas pipe, upstream of the first storage vessel, an impurity level of at least one given impurity in the gas produced in step a), and

e) controlling a three-way solenoid valve arranged on the main gas line upstream of the first storage vessel, and furthermore connected to the atmosphere via a vent line, so as to divert the gas present in the main pipe, upstream of the three-way solenoid valve, to the vent line when the impurity level measured in step d) is greater than or equal to a preset threshold level.

Depending on the case, the method of the invention may comprise one or more of the following technical characteristics:

-   -   in step e), the gas present in the main pipe, upstream of the         three-way solenoid valve, is diverted to the vent line and gas         is simultaneously stopped from being sent to the first storage         vessel, when the impurity level measured in step d) is greater         than or equal to a preset threshold level.     -   in step a), a purified gas is produced from a supply gas treated         in a gas purification unit comprising at least two adsorbers         operating alternately, and when an impurity level greater than         or equal to a preset threshold level is determined in the gas         produced by one of the said adsorbers, the production of the gas         by the said adsorber is stopped and the production of gas by the         other or an other of the said adsorbers is started.     -   gaseous flushing of the main pipe part containing an impurity         level greater than or equal to the preset threshold level with         purified gas is carried out and the gas flow thus generated is         discharged to the atmosphere via the vent line.     -   the gas to be purified is ambient air and the purified gas is         medical air or medical oxygen, that is to say with the         specifications of the European Pharmacopoeia, as explained         above.     -   the impurity or impurities are selected from NOx, SOx, COx,         water vapour and hydrocarbon vapours, in particular oil vapours.     -   the medical air produced contains (by volume) from 20.4% to         21.4% oxygen, at most 500 ppm CO₂, at most 5 ppm CO, at most 1         ppm SO₂, at most 2 ppm NO and NO₂, at most 67 ppm water, at most         0.1 mg/m³ oil, and nitrogen.     -   in step d), a gas analysis device is used in order to determine         the impurity level in the main gas pipe.     -   in step e), an operating device, such as a programmable         automaton, is used in order to control the three-way solenoid         valve, the said operating device acting in response to the         measurements taken by the gas analysis device.

BRIEF DESCRIPTION OF THE DRAWING

For a further understanding of the nature and objects for the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawing, in which like elements are given the same or analogous reference numbers and wherein:

FIG. 1, which represents the block diagram of an embodiment of a plant 100 for on-site production of medical gases, controlled by the operating method according to the invention, which plant 100 is connected to the network of pipes 30 of a hospital building.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described in more detail with reference to the appended FIG. 1, which represents the block diagram of an embodiment of a plant 100 for on-site production of medical gases, controlled by the operating method according to the invention, which plant 100 is connected to the network of pipes 30 of a hospital building or the like.

The gas produced here is medical air, that is to say purified air satisfying the specifications of the European Pharmacopoeia mentioned above. Nevertheless, such a plant 100 may be used for manufacturing other medical gases, for example medical oxygen from ambient air.

More precisely, in this embodiment, the on-site medical air production plant 100 comprises a gas purification unit 50 supplied by a gas compression unit 31, that is to say one or more air compressors taking in ambient air at atmospheric pressure (i.e. 1 atm) through their supply inlet 32 and delivering compressed air at a pressure higher than atmospheric pressure, for example at a pressure of between 1 bar and 80 bar absolute. This compressor or these compressors 31 may be one or more screw, piston, scroll or diaphragm compressors.

The compressed air supplies the gas purification unit 50, which here comprises two adsorbers 1, 2 operating in parallel according to cycles of the PSA type (Pressure Swing Adsorption) or TSA type (Temperature Swing Adsorption), that is to say one is in production phase while the other is in regeneration phase, and vice versa. Typically, the duration of a production cycle is between 1 and 30 minutes, approximately, preferably from less than 10 to 15 minutes.

These adsorbers each contain at least one bed of at least one adsorbent material, for example adsorbent materials such as zeolites, aluminas, active carbon, silica gel or any other molecular sieve capable of stopping the impurities present in ambient air.

Depending on the embodiment in question, the gas purification unit 50 may also comprise a single adsorber or more than 2 adsorbers 1, 2, for example at least 3 adsorbers.

These types of adsorbers 1, 2 and PSA or TSA cycle are well known and, in this regard, reference may furthermore be made for example to the documents EP-A-716274, EP-A-718024, EP-A-922482, GB-A-1551348, EP-A-930089.

In all cases, the adsorbers 1, 2 make it possible to eliminate all or some of the impurities which are possibly present in the ambient air to be purified or which have been introduced therein during the compression (at 31), in particular water vapour, oil vapours, SOx, COx and/or NOx, so as to produce a medical gas compliant with the Pharmacopoeia, in particular medical air compliant with the European Pharmacopoeia.

Next, the purified air (or any other medical gas) produced by the gas purification unit 50 is recovered in outlet conduits 9 which supply a main line 10 conveying gas, that is to say a pipe or a tube delivering gas, which is adapted and designed to convey the purified air produced in this way to a first storage vessel A, that is to say a buffer vessel, in which the purified medical air can be stored and homogenized before being sent to one or more consumer sites 30, such as a network of gas pipes passing through a hospital building in order to convey the medical air to the various rooms in which it is to be used, such as treatment rooms, emergency rooms, recovery rooms, bedrooms or any other any other location.

The main gas line 10 therefore fluidically connects the outlet (or outlets) 9 of the gas purification unit 50 to the said first storage vessel A so as to supply it with purified air coming from the two adsorbers 1, 2 of the gas purification unit 50.

The operation of the compressor or the compressors 31 and the purification cycles taking place in the gas purification unit 50 are controlled and monitored by an operating device 4, for example a programmable automaton or the like, connected to the gas purification unit 50 by electrical connections 8, such as electrical cables.

It should, however, be noted that communication between the various elements and devices of the plant, in particular with the automaton 4, could in general also take place via wireless links, for example via one or more wireless transmitter devices or systems such as radiofrequency (RF), Bluetooth, Zigbee, wifi, GSM or GPRS, and one or more receiver antennas for carrying out wireless transmissions of data adapted to the type of transmitter used.

Preferably, the automaton 4 or the like is programmed according to the requirements of the hospital site in question and can be reprogrammed if the requirements of the site change, for example.

In order to regulate and monitor the conveyance of gas in the main gas line 10, a solenoid valve VA is arranged on the said main line 10 between the gas purification unit 50 and the first storage vessel A. The solenoid valve VA is also controlled by the operating device 4 via an electrical connection 5, such as an electrical cable.

According to the present invention, the valve VA is a three-way solenoid valve, one of the ports of which is fluidically connected via a vent line 11 to the ambient atmosphere (at 12) where there is preferably a device for venting to the atmosphere, such as a vent valve (not represented), and the other two ports of which are fluidically connected to the main line 10.

The air produced by the gas purification unit 50 therefore passes through two of the ports of the solenoid valve VA, that is to say the first and second ports of the solenoid valve VA, when it passes normally through the said solenoid valve VA in the direction of the buffer vessel A where the purified gas can be stored.

Conversely, in the event of contamination of the line 10 upstream of the valve VA, this pollution can be expelled easily and effectively from the contaminated conduit portion of the main line 10, without the need for a total purge of the system upstream of the valve VA.

This is done conventionally by flushing the conduit portion polluted by impurities with pure air produced by the gas purification unit 50. The gas flow entraining the impurities is then discharged via the third port of the solenoid valve VA to the atmosphere, through the vent line 11 to the ambient atmosphere. In other words, the air produced by the gas purification unit 1, 2 will then entrain the pollutants with it and these will be disposed of to the atmosphere (at 12).

The 3-way solenoid valve VA therefore makes it possible not only to block any possible pollution on the main line 10 in order to confine it upstream of the solenoid valve VA, but also subsequently to discharge this pollution of the main line 10 to the outside (at 12) and thus to purge the main line 10 upstream of the valve VA.

This solution makes it possible to avoid shutting down the production process entirely and resorting to the backup 3, that is to say a reserve of pure gas, in the event of temporary pollution of the air taken in or created by the production line.

Furthermore, the first buffer vessel A makes it possible to take over the delivery of the purified gas, such as medical air, when the valve VA is in the vent position, that is to say when a purge of the line 10 is ongoing, so as here again to reduce the frequency of use of the backup source 3.

The first vessel A also makes it possible to protect the production unit 50 from consumption peaks, that is to say peaks in demand from the consumer sites 30, and to homogenize the air produced by the production unit.

The monitoring of the composition of the gas produced, such as purified air, delivered by the production unit 50 is carried out by means of a first gas analysis device D1, such as an analysis cabinet or any other suitable gas analyzer, the measurement line 29 of which is connected fluidically (at 28) to the main line 10, upstream of the 3-way solenoid valve VA.

This gas analysis device D1 is connected to the operating device 4 via an electrical connection 7, such as an electrical cable or the like, so as to transmit measurement signals and optionally other information thereto.

As a function of the signals received, the operating device 4 can retroact on the 3-way solenoid valve VA and preferably the other elements of the plant, such as production unit 50, compressor 31, etc., in order to trigger a purge of the line 10 when pollution is detected.

More precisely, in order to evaluate the reliability of the method and of the production plant, the quality of the air produced is analyzed using the analysis cabinet D1, in particular the levels of H₂O, CO₂ and oil vapour. Complementary monitoring variables (for example temperature, pressure, vibrations, etc.) are furthermore collected from the plant.

The analysis results as well as the monitoring variables are then processed by the operating device 4, such as an automaton, on the basis of statistical process control (SPC) in order to define the reliability of the production process.

The processing of the data is carried out for each of the production lines, that is to say for each of the adsorbers 1, 2 of the production unit 50 as well as the compressors 31, on the basis of conventional control elements, such as aptitude indicators of the production process, control chart of the variables, average, control limits, trend analysis of the variables, etc.

On the basis of the results and the predefined parameters, it is then possible to determine whether or not the manufacturing process is reliable.

Thus, when the operating device 4 determines that the level of one or more impurities in the main gas pipe 10, in particular upstream of the first storage vessel A, is greater than or equal to a preset threshold level, for example the maximum values set by the European Pharmacopoeia as regards the level of water vapour, or oil vapours, SOx, COx and/or NOx, the said operating device 4 controls the three-way solenoid valve VA so as to divert the gas present in the main pipe 10, in particular the gas present upstream of the three-way solenoid valve VA, to the vent line 11 and thus purge the main line 10 of the impure, that is to say noncompliant, the gas contained therein.

In this case, i.e. when the manufacturing process is not reliable, or no longer reliable, the production line in question, that is to say the adsorbers 1 or 2 and the associated compressor 31, is shut down and the second line takes over for producing purified air, while the other line is regenerated, reinitialized and/or undergoes a maintenance operation.

In other words, in the event of excessive impurity levels, the gas present in the main pipe 10 is diverted to the vent line 11 and gas is simultaneously stopped being sent to the first storage vessel A.

At this time, the production of the gas by the adsorber 1 or 2 in question is stopped and production of gas by the other adsorber 1 or 2, respectively, of the production unit 50 is started.

This gas produced by the other adsorber will then be used to carry out gaseous flushing of the part of the main pipe 10 containing the impurity level greater than or equal to the preset threshold level then will subsequently be discharged to the atmosphere as a result of the gas flow thus generated, via the vent line 11.

When the pipe 10 has been purged and the impurity level has returned to normal, the operating device 4 will control the 3-way solenoid valve VA in order to stop the purge and allow gas again to be sent to the vessels A, B and/or C located downstream.

The gas produced in this way is then subjected to monitoring as before.

In the event of unreliability of the second line as well, the system then switches to the backup source 3. Specifically, the plant also comprises a backup line 40 fluidically connecting a backup source 3, such as a backup reservoir containing medical air, to the gas consumer sites 30, directly or indirectly, that is to say by being connected at 23 to the main gas line 10 or to a secondary line 20.

The secondary line 20 is in fact another gas line arranged in parallel with the main line 10 and used as an alternative passage for the gas coming from the vessel A, for example, and/or from the production unit 50, when the main line 10 is out of use, for example contaminated and/or undergoing a maintenance operation.

In other words, the main gas line 10 branches (at 21) downstream of the first vessel A into a secondary line 20. The latter 20 is therefore fluidically connected on its upstream side (at 21) to the said main line 10 and, by its downstream end, to at least one gas consumer site (30), directly or indirectly, that is to say by being connected (at 22) to the main gas line 10.

Furthermore line 10 also comprises a second buffer vessel B for storing purified gas, located between the first vessel A and the gas consumer site or sites, such as a network of pipes 30 of a hospital building, and the secondary line 20 in turn comprises a third vessel C for storing purified gas.

The vessels B, C are used to supply the consumer site or sites 30 with respiratory gas. In fact, the vessels B and C are used to provide medical air in alternation, that is to say while one vessel (for example B) is being filled or analyzed for compliance, the second (respectively C) delivers the gas to the hospital network 30, or vice versa.

In general, maintenance of the plant 100 is triggered by the automaton 4 on an anticipatory basis when the production parameters of one or both production units 1, 2 reach a predetermined threshold.

It will furthermore be noted that 2-way solenoid valves are arranged on the main line 10 and the secondary line 20. More precisely, a first solenoid valve V1 is arranged between the first vessel A and the second vessel B, and a second solenoid valve V3 is arranged between the first vessel A and the third vessel C for storing purified gas.

Furthermore, a third solenoid valve V2 is arranged downstream of the second vessel B and a fourth solenoid valve V4 is arranged downstream of the third vessel C. These 2-way solenoid valves are controlled by the operating device 4 via electrical connections 6, 37, such as cables or the like, and make it possible to control the passage of the gas through the lines 10 and 20 and therefore to divide the pipes 10, 20 into well-determined sections, and also to manage and/or operate the gas inlets and/or outlets of the vessels B and C.

The plant 100 furthermore comprises a first purge line 13 fluidically connected by its upstream end 24 to the main line 10, preferably downstream of the second vessel B, and by its downstream end 25 to the vent line 11, as well as a second purge line 14 fluidically connected by its upstream end 26 to the secondary line 20, preferably downstream of the third vessel C, and by its downstream end 27 to the vent line 11.

The first purge line 13 comprises a fifth solenoid valve V7 and the second purge line 14 comprises a sixth solenoid valve V8 used to control the passage of the gas to the vent line 11. The operating device 4 also controls the solenoid valves V7, V8 via electrical connections 37.

These purge lines 13, 14 make it possible to purge the portions of lines 10, 20 as well as the vessels B and C, respectively, located upstream of the solenoid valves V2 and V4, respectively.

A second gas analysis device D2, such as an analysis cabinet or the like, is provided and includes at least one second measurement line 36, branching into two subsections 36 a, 36 b, which is fluidically connected (at 34, 35) to the main line 10 and to the secondary line 20, in particular by means of the subsections 36 a, 36 b. Preferably, the second measurement line 36, 36 a, 36 b comprises a seventh V5 and/or an eighth V6 solenoid valve.

This second gas analysis device D2 makes it possible to determine the composition of the gas circulating in the main 10 and secondary 20 lines, downstream of the vessels B, C, that is to say it makes it possible to analyze discontinuously the gas taken from the vessels B and C. As before, this second gas analysis device D2 cooperates with the operating device 4, which itself controls the solenoid valves V5, V6 via electrical connections 37.

The electrical supply of the plant 100 is carried out conventionally by current from the mains, for example at a voltage of between 1 and 600 V, typically 24 V, 230 V or 400 V.

If need be, measurement means (not shown) may be provided in order to determine the pressure of the medical air contained in the vessels A, B, C for storage and homogenization of the gas and optionally retroact via the operating device 4 on the compression unit 31 and/or the production unit 50 so as to regulate the production of the gas, such as air, by taking into account the pressure (or pressures) thus measured. For example, the operating means 4 may be programmed in order to cause shutdown of the flow source 31 and/or triggering of an audio and/or visual alarm, when a pressure sensor arranged at the buffer vessel A detects a pressure or a pressure difference greater than or, conversely, less than a preset threshold value. This type of pressure regulation is well known and will not be described in detail here.

Furthermore, in order to ensure even more effective purification of the air taken in by the compressor 31, one (or more) mechanical filtration devices (not represented in detail) may be provided, arranged at one or more sites between the air source 31 and the hospital network 30. For example, the compression unit may comprise one or more filters at the inlet 32 and/or outlet 33 in order to retain the dust contained in the ambient air and the condensates due to the compression, for example cyclone filters or separators, micron filters or the like.

In general, the plant 100 of the invention for production of medical air on-site, that is to say in a hospital building or the like, therefore employs a three-way solenoid valve adapted to discharge product gas contaminated by impurities to the atmosphere via a purge line connected to one of the ports of the solenoid valve VA, in response to detection of the said contamination by an analysis device D1 cooperating with the operating device 4.

The medical air production plant 100 of the invention may be used directly on the site where the gas is used, that is to say directly in a hospital building or the like. It may therefore be installed directly in a room of the hospital building or outside the said building or in containers, and connected to the network 30 of pipes conveying the gas inside the building. 

What is claimed is:
 1. An on-site medical gas production plant (100), comprising: a gas purification unit (50) configured to produce a purified gas from a less pure supply gas source, a first vessel (A) for storing the purified gas, and a main gas line (10) fluidically connecting the gas purification unit (50) to the first storage vessel (A) so as to supply the said first storage vessel (A) with the purified gas coming from the gas purification unit (50), wherein the main gas line furthermore comprises: a three-way solenoid valve (VA) arranged on the main gas line (10) between the gas purification unit (50) and the first storage vessel (A), and furthermore connected to the atmosphere (at 12) via a vent line (11), an operating device (4) which controls at least one three-way solenoid valve (VA), at least a first gas analysis device (D1) of which a first measurement line (29) is fluidically connected (at 28) to the main line (10), upstream of the three-way solenoid valve (VA), and which is electrically connected to the operating device (4), and in which the operating device (4) is designed and adapted to act on the three-way solenoid valve (VA) in response to a signal received from the gas analysis device (D1), so as to divert a gas present in the main pipe (10) to pass to the vent line (11) when the signal received from the gas analysis device (D1) corresponds to a contamination signal based on an analysis of the gas in the main pipe (10), and simultaneously to prevent the gas present in the main pipe (10) from being sent to the said first storage vessel (A).
 2. The plant according to claim 1, wherein a gas compression unit (31) is configured to supply the gas purification unit (50) with a gas to be purified at a pressure of more than 1 bar absolute,
 3. The plant according to claim 2, wherein the gas compression unit (31) comprises at least one screw, piston, scroll or diaphragm compressor.
 4. The plant according to claim 1, wherein the gas purification unit (50) comprises at least one adsorber (1, 2) containing at least one bed of at least one adsorbent material.
 5. The plant according to claim 1, wherein the gas purification unit (50) comprises at least two adsorbers (1, 2) configured to operate alternately.
 6. The plant according to claim 1, wherein the gas purification unit (50) comprises at least two adsorbers (1, 2) configured to operate alternately, and the operating device (4) is designed and adapted to act on the gas purification unit (50) and/or the gas compression unit (31) so as to stop any production of gas by the adsorber (1, 2) which was in operation at the time when the gas analysis device (D1) transmitted the contamination signal to the operating device (4).
 7. The plant according to claim 1, wherein the gas purification unit (50) comprises at least two adsorbers (1, 2) configured to operate alternately, and the operating device (4) is designed and adapted to act on the gas purification unit (50) and/or the gas compression unit (31) so as to start production of gas by the adsorber (1, 2) which was not in operation at the time when the gas analysis device (D1) transmitted the contamination signal to the operating device (4).
 8. The plant according to claim 1, wherein the operating device (4) is designed and adapted to act on the three-way solenoid valve (VA) in response to a signal received from the gas analysis device (D1), so as to stop the gas present in the main pipe (10) from passing to the vent line (11) when the signal received from the gas analysis device (D1) corresponds to a compliant gas signal, and simultaneously to allow gas to be sent to the first storage vessel (A).
 9. Method for operating an on-site medical gas production plant (100), the plant comprising: a gas purification unit (50) configured to produce a purified gas from a less pure supply gas source, a first vessel (A) for storing the purified gas, and a main gas line (10) fluidically connecting the gas purification unit (50) to the first storage vessel (A) so as to supply the said first storage vessel (A) with the purified gas coming from the gas purification unit (50), wherein the main gas line furthermore comprises: a three-way solenoid valve (VA) arranged on the main gas line (10) between the gas purification unit (50) and the first storage vessel (A), and furthermore connected to the atmosphere (at 12) via a vent line (11), an operating device (4) which controls at least one three-way solenoid valve (VA), at least a first gas analysis device (D1) of which a first measurement line (29) is fluidically connected (at 28) to the main line (10), upstream of the three-way solenoid valve (VA), and which is electrically connected to the operating device (4), and in which the operating device (4) is designed and adapted to act on the three-way solenoid valve (VA) in response to a signal received from the gas analysis device (D1), so as to divert a gas present in the main pipe (10) to pass to the vent line (11) when the signal received from the gas analysis device (D1) corresponds to a contamination signal based on an analysis of the gas in the main pipe (10), and simultaneously to prevent the gas present in the main pipe (10) from being sent to the said first storage vessel (A); the method comprising the steps of: a) producing a purified gas from a from a less pure supply gas source, b) transporting the purified gas obtained in step a) in a main gas pipe (10), c) storing at least a part of the purified gas in a first vessel (A) for storing gas supplied by the main gas pipe (10), d) determining in the main gas pipe (10), upstream of the first storage vessel (A), an impurity level of at least one given impurity in the gas produced in step a), and e) controlling a three-way solenoid valve (VA) arranged on the main gas line (10) upstream of the first storage vessel (A), and furthermore connected to the atmosphere (at 12) via a vent line (11), so as to divert the gas present in the main pipe (10), upstream of the three-way solenoid valve (VA), to the vent line (11) when the impurity level measured in step d) is greater than or equal to a preset threshold level.
 10. The method according to claim 9, wherein in step e), the gas present in the main pipe (10), upstream of the three-way solenoid valve (VA), is diverted to the vent line (11) and gas is simultaneously stopped from being sent to the first storage vessel (A), when the impurity level measured in step d) is greater than or equal to a preset threshold level.
 11. The method according to claim 9, wherein: in step a), the gas purification unit (50) comprises at least two adsorbers (1, 2) operating alternately, and when an impurity level greater than or equal to a preset threshold level is determined in the gas produced by one of the adsorbers, the production of the gas by the adsorber is stopped and the production of purified gas by another of the adsorber(s) is started.
 12. The method according to claim 10, wherein a gaseous flushing step of the main pipe (10) containing an impurity level greater than or equal to the preset threshold level with purified gas is carried out and the gas flow thus generated is discharged to the atmosphere via the vent line (11).
 13. The method of claim 9, wherein less pure supply gas source to be purified is ambient air and the purified gas is medical air or medical oxygen.
 14. The method of claim 9, wherein the impurity or impurities are selected from NOx, SOx, COx, water vapour, hydrocarbon vapours, or combinations thereof.
 15. The method of claim 13, wherein the medical air produced contains (by volume) from 20.4% to 21.4% oxygen, at most 500 ppm CO₂, at most 5 ppm CO, at most 1 ppm SO₂, at most 2 ppm NO and NO₂, at most 67 ppm water, at most 0.1 mg/m³ oil, and nitrogen.
 16. The method of claim 13, wherein in step d), a gas analysis device (D1) determines the impurity level in the gas in the main gas pipe (10).
 17. The method of claim 16, wherein in step e), an operating device (4) controls the three-way solenoid valve (VA), the operating device (4) acting in response to the measurements taken by the gas analysis device (D1). 